Honda Power Unit Hardware & Software

[MrPotatoHead]

You forget the large periods of full throttle. You rely on your wastegates, your MGU-H to harvest, and any excess boost pressure, instead of being bled to the atmosphere, is accumulated, this way you gain work from both turbine and compressor. Clearly these compressors are capable of delivering more than enough air, this way you can run the turbo at high speeds at all times without wasting anything.

I have to stop you right there. In steady conditions, no boost spikes or excess energy will be coming from the Compressor/turbine/MGUH. It is harvested to the battery according to ECU mapping. There is no excess boost pressure except for quick throttle blips and quick downshifts - where feed forward control algorithms would be used to predict these boost spikes; and I am only guessing that there is finite control in doing this. So, in that sense it is much more efficient to use the MGUH with a high priority if you can prevent boost spikes.
I only was entertaining your idea of using an air motor to scavenge compressed air for those transient conditions when boost spikes are inevitable, but I do not agree with your view that the excess boost is in ample supply. Producing excess boost just to recover it back is not efficient. Better to only produce as much boost as you need.

That was the thinking that steered Honda to mounting the turbo within the V, we know how that turned out.

No the problem is their calculations were way off so they needed a bigger compressor and had no more space for it there.

[godlameroso]

How does that contradict what I said? It's clear these engines are designed to run on air dilution, they're also high compression engines. The compressor is easily able to flow more air than the fuel flow rate requires, so you either use the wastegates and MGU-H alone to keep shaft RPM well below the max RPM limit, or you harvest while trying to maintain the shaft speed at the rpm limit. However, at this point your compressor is producing excess boost pressure, so you have to use the compressor bypass to limit pressure if you are trying to maintain max turbine RPM for efficiency and harvesting purposes.

[roon]

"as much boost as you need"

What would the upper limit for air-fuel ratios be? Is the limit:

• power required by the compressor becomes too great
• ability for the air to be optimally heated in-cylinder

[hurril]

How does that contradict what I said? It's clear these engines are designed to run on air dilution, they're also high compression engines. The compressor is easily able to flow more air than the fuel flow rate requires, so you either use the wastegates and MGU-H alone to keep shaft RPM well below the max RPM limit, or you harvest while trying to maintain the shaft speed at the rpm limit. However, at this point your compressor is producing excess boost pressure, so you have to use the compressor bypass to limit pressure if you are trying to maintain max turbine RPM for efficiency and harvesting purposes.

I think you're conflating the fact that these engines run very lean, as in: they run with much higher lambda values than your ordinary (turbo) engine would, with the idea that somehow they have excess air. They don't (have excess air.) They produce their power at a different "parameter point" compared to more ordinary engines, one that involves perhaps twice as much air.

Getting twice as much air through the same tiny engine implies a number of things; a huge pressure ratio for one and the ability to pump a lot of air. Both of these things, in turn, imply a number of things when it comes to the nature of both the turbine and the compressor and those things, in turn, imply things about the RPM(-range) of the turbo axle which, in turn, ... etc: you get the picture.

The power output of the turbine is quite the percentage of the power output of the ICE itself. Compare that to an engine of any size but that puts out the same amount of power. What does this mean?

[PlatinumZealot]

Dont want to jump in between your exchange. But i have to highlight something related to this.
Anyone ever looked on some diesel engine's horspower per liter and see something like 500 horspower from 24 liters and then you laugh out loud at its "shitty" performance? Hah. Well. They operate at a very diluted air fuel ratio to give the best efficiency. All that cyilinder volume is needed especially if the engine is naturally aspirated diesel. For turbocharged diesels now it usually means higher boost pressures to get that dilution. I am no expert, but it is just how those engines are designed.

[hurril]

Dont want to jump in between your exchange. But i have to highlight something related to this.
Anyone ever looked on some diesel engine's horspower per liter and see something like 500 horspower from 24 liters and then you laugh out loud at its "shitty" performance? Hah. Well. They operate at a very diluted air fuel ratio to give the best efficiency. All that cyilinder volume is needed especially if the engine is naturally aspirated diesel. For turbocharged diesels now it usually means higher boost pressures to get that dilution. I am no expert, but it is just how those engines are designed.

Well, that and because torque

[Tommy Cookers]

the upper limit of the air:fuel ratio is determined by ? ......

the combustibility of the fuel and by turbine and compressor efficiencies at these high boosts
it's no accident that the rules dictate this one particular combination of AFR and boost
if the compressor and turbine efficiencies were even 2% lower the MGU-H recovery power would be much lower
(these efficiencies achieved in F1 would be rather wasted on a turbocharged engine - just giving more wastegating)

if propane fuelled (or hydrogen fuelled) they could use much higher (or very much higher) AFR
(propane etc can also be used for pre-chamber initiation for combustion of gasoline main fuel to raise useable AFR)
such higher AFR needs higher boost and so more than one stage of compressor and turbine (or a bigger engine/bigger losses)

high boost means high work in-cylinder during compression so friction work rises
ultimately this limits the raising of AFR - otherwise you'd have a hydrogen engine with no cooling needed for combustion heat

in current F1 the dilution of (fuel) heat from using 'excess' air greatly reduces heat loss to coolant and benefits ICE power

btw
combustion efficiency means the % of the total fuel heat that is liberated in the cylinder - it is c. 95%
(unfortunately one source seems to use CE as the % of total fuel heat turned into work at the piston crowns)

[dren]

That was the thinking that steered Honda to mounting the turbo within the V, we know how that turned out.

No the problem is their calculations were way off so they needed a bigger compressor and had no more space for it there.

Were the calculations way off or was it a packaging compromise? I would guess the later, but I have no clue.

[MrPotatoHead]

That was the thinking that steered Honda to mounting the turbo within the V, we know how that turned out.

No the problem is their calculations were way off so they needed a bigger compressor and had no more space for it there.

Were the calculations way off or was it a packaging compromise? I would guess the later, but I have no clue.

I do not know for sure but I suspect a combination of both. But I think the former was a larger factor.
People like to make a big deal of the McLaren "size 0" thing, but the reality is all of the engines are extremely compact and packaged very tightly.

[dren]

No the problem is their calculations were way off so they needed a bigger compressor and had no more space for it there.

Were the calculations way off or was it a packaging compromise? I would guess the later, but I have no clue.

I do not know for sure but I suspect a combination of both. But I think the former was a larger factor.
People like to make a big deal of the McLaren "size 0" thing, but the reality is all of the engines are extremely compact and packaged very tightly.

I agree, all of the PUs are very compact, even with different layouts. I've read claims that the Honda PU is 25% smaller, which is comical based on the regulations! I can see Honda being fixated on fitting the compressor in the V once that layout was decided. Plus, with the combustion concepts they were using with their first PU, the compromise might not have been that large to house the compressor in the V. We know the ICE was down on power, but the ERS was quite lacking. As Honda started exploring more turbine power for the MGUH, everything else compounds. Of course we can only guess; it'd be great if we had actual design parameters.

[godlameroso]

How does that contradict what I said? It's clear these engines are designed to run on air dilution, they're also high compression engines. The compressor is easily able to flow more air than the fuel flow rate requires, so you either use the wastegates and MGU-H alone to keep shaft RPM well below the max RPM limit, or you harvest while trying to maintain the shaft speed at the rpm limit. However, at this point your compressor is producing excess boost pressure, so you have to use the compressor bypass to limit pressure if you are trying to maintain max turbine RPM for efficiency and harvesting purposes.

I think you're conflating the fact that these engines run very lean, as in: they run with much higher lambda values than your ordinary (turbo) engine would, with the idea that somehow they have excess air. They don't (have excess air.) They produce their power at a different "parameter point" compared to more ordinary engines, one that involves perhaps twice as much air.

Getting twice as much air through the same tiny engine implies a number of things; a huge pressure ratio for one and the ability to pump a lot of air. Both of these things, in turn, imply a number of things when it comes to the nature of both the turbine and the compressor and those things, in turn, imply things about the RPM(-range) of the turbo axle which, in turn, ... etc: you get the picture.

The power output of the turbine is quite the percentage of the power output of the ICE itself. Compare that to an engine of any size but that puts out the same amount of power. What does this mean?

That's fine I understand you have design considerations. If you were designing a turbo for these engines, would you try to balance out the compressor and turbine PR? Or would you bias it towards the compressor or turbine? In other words do you want a big high flowing compressor, and a smaller more responsive turbine while using MGU-H and wastegates? Or do you go for a more balanced approach, and attempt to match turbine back pressure to the compressor requirements? We know no one uses small compressor in relation to the turbine, so that narrows down your choices.

My question I guess boils down to which side do you want operating at max speed. If the compressor is capable of 4+ bar at less than 125k rpm shaft speed, then that means shaft speed will be lower than that, which means less shaft speed for the MGU-H to harvest. On the other hand if the turbine is at max speed since the compressor is on the same shaft, the compressor is either pumping out excess air, or it's fallen out of its efficiency island.

Neither scenario is ideal, in one you have to purge boost pressure, in the other the turbo is being inefficient.

[hurril]

How does that contradict what I said? It's clear these engines are designed to run on air dilution, they're also high compression engines. The compressor is easily able to flow more air than the fuel flow rate requires, so you either use the wastegates and MGU-H alone to keep shaft RPM well below the max RPM limit, or you harvest while trying to maintain the shaft speed at the rpm limit. However, at this point your compressor is producing excess boost pressure, so you have to use the compressor bypass to limit pressure if you are trying to maintain max turbine RPM for efficiency and harvesting purposes.

I think you're conflating the fact that these engines run very lean, as in: they run with much higher lambda values than your ordinary (turbo) engine would, with the idea that somehow they have excess air. They don't (have excess air.) They produce their power at a different "parameter point" compared to more ordinary engines, one that involves perhaps twice as much air.

Getting twice as much air through the same tiny engine implies a number of things; a huge pressure ratio for one and the ability to pump a lot of air. Both of these things, in turn, imply a number of things when it comes to the nature of both the turbine and the compressor and those things, in turn, imply things about the RPM(-range) of the turbo axle which, in turn, ... etc: you get the picture.

The power output of the turbine is quite the percentage of the power output of the ICE itself. Compare that to an engine of any size but that puts out the same amount of power. What does this mean?

That's fine I understand you have design considerations. If you were designing a turbo for these engines, would you try to balance out the compressor and turbine PR? Or would you bias it towards the compressor or turbine? In other words do you want a big high flowing compressor, and a smaller more responsive turbine while using MGU-H and wastegates? Or do you go for a more balanced approach, and attempt to match turbine back pressure to the compressor requirements? We know no one uses small compressor in relation to the turbine, so that narrows down your choices.

My question I guess boils down to which side do you want operating at max speed. If the compressor is capable of 4+ bar at less than 125k rpm shaft speed, then that means shaft speed will be lower than that, which means less shaft speed for the MGU-H to harvest. On the other hand if the turbine is at max speed since the compressor is on the same shaft, the compressor is either pumping out excess air, or it's fallen out of its efficiency island.

Neither scenario is ideal, in one you have to purge boost pressure, in the other the turbo is being inefficient.

This is too one-dimensional in its approach. You can (and want to) increase the throughput, you do that by increasing both sides but you have to do it in a way that does not compromise on the pressure ratio. A "bigger house" can flow more air but also "leaks" more air/ gas unless you do something to the impellers as well. All of these things have down- and upstream consequences.

There's no "opting for a smaller turbine" in order that the engine be more responsive in this sort of formula. At least not in the simple sense.

My take is that you begin with calculating how much gas (air/ fluid) can be put through the engine without causing it to explode/ break over time. How much gas as a function of RPM of the engine so that you can determine some sort of working range. This range in gas throughput, temperature and pressure is what you build the turbine from and also what determines how much work can be extracted from it. This work needs to cover the workload of the compressor and the _desired_ workload of the MGU-h.

Since there's a positive feedback loop going on, like compound interest, a reduced turbine capacity causes everything else to become that much worse.

Also: can the ICE actually use a given gas flow or is a slightly smaller one just as good enough when it comes to effective and efficient combustion. If you can reduce the work needed for compressing air, then that is work that the MGU-h can use instead. A lot of this also comes down to aerodynamics of the engine internals.

Shaft speed and just pressure don't tell the whole story. You can make just as much power on any RPM and 4 bar does not tell us how much air is flowed. Not without knowing everything else. A set of tyres could have 4 bars in them and there is nothing flowing there; you could have a monstrous low-pressure turbo that only ever puts out 1bar.

The RPM is interesting as a tool or a means to and end in turbine wheel construction. And of course: any given appliance is going to represent more energy at a higher RPM than it would at a lower and thusly require more power to accelerate or decelerate it, but that is beside the point. All of these parameters go together to make a whole and this is also what I was alluding to in the post you replied to: these engines run at a different "parameter point" (in lack of a better way to put it.)

[dren]

It's total PU efficiency to be focused on, not just one particular area. It seemed like Honda focused on their ICE and 'slapped on' an ERS with their first PU in 2015. That might not be the case, but seemed like it.

[godlameroso]

I think you're conflating the fact that these engines run very lean, as in: they run with much higher lambda values than your ordinary (turbo) engine would, with the idea that somehow they have excess air. They don't (have excess air.) They produce their power at a different "parameter point" compared to more ordinary engines, one that involves perhaps twice as much air.

Getting twice as much air through the same tiny engine implies a number of things; a huge pressure ratio for one and the ability to pump a lot of air. Both of these things, in turn, imply a number of things when it comes to the nature of both the turbine and the compressor and those things, in turn, imply things about the RPM(-range) of the turbo axle which, in turn, ... etc: you get the picture.

The power output of the turbine is quite the percentage of the power output of the ICE itself. Compare that to an engine of any size but that puts out the same amount of power. What does this mean?

That's fine I understand you have design considerations. If you were designing a turbo for these engines, would you try to balance out the compressor and turbine PR? Or would you bias it towards the compressor or turbine? In other words do you want a big high flowing compressor, and a smaller more responsive turbine while using MGU-H and wastegates? Or do you go for a more balanced approach, and attempt to match turbine back pressure to the compressor requirements? We know no one uses small compressor in relation to the turbine, so that narrows down your choices.

My question I guess boils down to which side do you want operating at max speed. If the compressor is capable of 4+ bar at less than 125k rpm shaft speed, then that means shaft speed will be lower than that, which means less shaft speed for the MGU-H to harvest. On the other hand if the turbine is at max speed since the compressor is on the same shaft, the compressor is either pumping out excess air, or it's fallen out of its efficiency island.

Neither scenario is ideal, in one you have to purge boost pressure, in the other the turbo is being inefficient.

This is too one-dimensional in its approach. You can (and want to) increase the throughput, you do that by increasing both sides but you have to do it in a way that does not compromise on the pressure ratio. A "bigger house" can flow more air but also "leaks" more air/ gas unless you do something to the impellers as well. All of these things have down- and upstream consequences.

There's no "opting for a smaller turbine" in order that the engine be more responsive in this sort of formula. At least not in the simple sense.

My take is that you begin with calculating how much gas (air/ fluid) can be put through the engine without causing it to explode/ break over time. How much gas as a function of RPM of the engine so that you can determine some sort of working range. This range in gas throughput, temperature and pressure is what you build the turbine from and also what determines how much work can be extracted from it. This work needs to cover the workload of the compressor and the _desired_ workload of the MGU-h.

Since there's a positive feedback loop going on, like compound interest, a reduced turbine capacity causes everything else to become that much worse.

Also: can the ICE actually use a given gas flow or is a slightly smaller one just as good enough when it comes to effective and efficient combustion. If you can reduce the work needed for compressing air, then that is work that the MGU-h can use instead. A lot of this also comes down to aerodynamics of the engine internals.

Shaft speed and just pressure don't tell the whole story. You can make just as much power on any RPM and 4 bar does not tell us how much air is flowed. Not without knowing everything else. A set of tyres could have 4 bars in them and there is nothing flowing there; you could have a monstrous low-pressure turbo that only ever puts out 1bar.

The RPM is interesting as a tool or a means to and end in turbine wheel construction. And of course: any given appliance is going to represent more energy at a higher RPM than it would at a lower and thusly require more power to accelerate or decelerate it, but that is beside the point. All of these parameters go together to make a whole and this is also what I was alluding to in the post you replied to: these engines run at a different "parameter point" (in lack of a better way to put it.)

So in essence, this makes turbo design even more difficult, not just housing, but blade geometry, number of blades, how they all interact with the combustion process at various engine loads and engine RPM, and the ERS.

I suppose once the combustion trickery is developed then it becomes a small increments game. Tweaking things methodically to gain a little efficiency here, and there, and it's only after various insignificant steps have been made that they can be taken together as a noticeable step forward.

[hurril]

So in essence, this makes turbo design even more difficult, not just housing, but blade geometry, number of blades, how they all interact with the combustion process at various engine loads and engine RPM, and the ERS.

I suppose once the combustion trickery is developed then it becomes a small increments game. Tweaking things methodically to gain a little efficiency here, and there, and it's only after various insignificant steps have been made that they can be taken together as a noticeable step forward.

Yes but I'm thinking that even fairly small changes will have a nice pay back because of the feedback nature of everything in an efficiency formula.